Mitigation of Sulfur Poisoning of Ni/Zirconia SOFC Anodes by Antimony and Tin

Abstract

Surface Sb/Ni and Sn/Ni alloys were found to efficiently minimize the negative effects of sulfur on the performance of Ni/zirconia anode-supported solid oxide fuel cells (SOFC). Prior to operating on fuel gas containing low concentrations of H2S, the nickel/ zirconia anodes were briefly exposed to antimony or tin vapor, which only slightly affected the SOFC performance. During the subsequent exposures to 1 and 5 parts per million H2S, increases in anodic polarization losses were minimal compared to those observed for the standard nickel/zirconia anodes. Post-test x-ray photoelectron spectroscopy analyses showed that Sb and Sn tended to segregate to the surface of Ni particles, and further confirmed a significant reduction of adsorbed sulfur on the Ni surface in Ni–Sn and Ni–Sb samples compared to the Ni. The effect may be the result of weaker sulfur adsorption on bimetallic surfaces, adsorption site competition between sulfur and Sb or Sn on Ni, or other factors. The use of dilute binary alloys of Ni–Sb or Ni–Sn in the place of Ni, or brief exposure to Sb or Sn vapor, may be an effective means to counteract the effects of sulfur poisoning in SOFC anodes and Ni catalysts. Other advantages, including the suppression of coking, are also expected.